You shouldn't have the power to compel people to go along with your ideas. So, for example, you think everybody should abstain from alcohol. Great - persuade people instead of outlawing it, because nobody should have the power to outlaw it. It shouldn't be a matter of voting on who gets that power over everybody, because nobody should have it.
Otto von Bismarck once said that "Die Politik ist die Lehre vom Möglichen", which can be translated as "politics is the science of achieving the possible". It may be better to persuade people to abstain from alcohol instead of just outlawing it (in fact, I have no doubts that what you say is true), but it would require so many resources (human, financial or whatever) that it would actually be more damaging in other parts than useful in just one. So outright outlawing alcohol may actually turn out to be the best option available, taking into account all possible consequences and effects...